As the Army closes in on renegade Confederates who refuse to abide by Civil War peace agreement, peaceful veterinarian Gil Hanley (Sterling Hayden) finds himself caught between these unforgiving combatants. When Hanley innocently treats the injuries of notorious Confederate outlaw Vern Brechene (James Anderson), he is unfairly accused of assisting a wanted outlaw. Railroaded in a military court, Hanley is imprisoned in the wretched Army prison in Hellgate, New Mexico, under the control of renegade-hating commander, Lieutenant Tod Voorhees (Ward Bond). With no fresh water or supplies, Hanley strikes up an uneasy partnership with fellow prisoner, Redfield (James Arness), to break out...